active_record_comparer.rb

class ActiveRecordComparer
  def initialize(original, new)
    @original = original
    @new = new
  end

  def method_missing(m, *arg)
    puts arg
    @original = @original.send(m, *arg)
    @new = @new.send(m, *arg)
    if @original.class != @new.class
      fail "classes don't match"
    end
    if @original.class != ActiveRecord::Relation
      if @original != @new
        fail "results don't match. Original: #{@original.inspect}, New: #{@new.inspect}"
      end
      return @original
    end
    self
  end
end

# Use:
#
# In Organization user identity class:
# def applicants
#   ActiveRecordComparer(self.old_applicants_method, self.new_applicants_method)
# end
#
# In client code:
# applicants.application_status_of("In Progress")
#
# I think it would raise a failure because they don't match. Which would make regression testing more likely to catch problems.

def method_missing(arg)
   @original = @original.send(arg)
   @new = @new.send(arg)
   if [@original, @new].all? { |k| k.kind_of?(ActiveRecord::Relation) }
    new(@original, @new)
  elsif @original == @new
    @new
  else
    raise 'The results do not match'
  end
end